Historically, printed games have existed based on words, numbers, and/or characters. One format provides a typically rectangular grid marked off by intersecting horizontal and vertical lines to produce cells or boxes. In one conventional approach, a starting (unsolved) puzzle includes characters in all of the cells, and a player of the game examines the array of characters to solve the game. In another conventional approach, the starting puzzle includes cells that are blank, and a player examines the puzzle to determine how to fill in the blank cells.
One well known approach is that taken by Sudoku games. In a typical Sudoku game, a grid is a nine by nine square, and the characters for the game are the digits one through nine (1-9). Each horizontal row in the grid contains nine digits, and each vertical row in the grid contains nine digits (in the solved puzzle). The square grid is further divided into nine subgrids, and each subgrid is a three by three square that contains nine digits (in the solved puzzle). A starting puzzle is provided that has digits presented in some cells, and some cells are blank. The game is played by adding a digit for each blank cell. When the puzzle is completed and solved, each digit must be unique in three ways. For a particular cell with a digit, the digit must be unique for its horizontal row; that is, there cannot be a duplicate of the digit in its horizontal row. The particular digit must also be unique for its vertical row. Furthermore, the particular digit must be unique for its subgrid. Provisional patent application U.S. 61/200,740, titled “Letter Placement Puzzle,” and filed Dec. 4, 2008 by Jefferson W. Cleghorn, describes a puzzle based on a grid having twenty-five-by-twenty-five (25×25) cells for letters. The grid is divided into 25 subgrids, with each subgrid having dimensions of five-by-five (5×5) cells. Each letter entered into a cell in the solved puzzle must be unique for its horizontal row, its vertical row, and its subgrid.